The present invention pertains to an improved valve and more particularly pertains to a valve having enhanced rangeability and a logarithmic flow characteristic. The valves of the invention are particularly well adapted to the valving of dry solid particulate materials having high flowing densities (for example, fluidized solids such as the fluidized catalysts flowed through dense-phase standpipes utilized in fluid catalytic cracking units), and slurries of coal or other abrasive particulate solids in liquids.
The prior art discloses valve structures specifically designed for handling fluidized solids, other solid particulates and/or slurries, and shows an awareness of the problems of flow characteristics and of wear of the component parts of such valves by the handling of abrasive solid materials.
Bulletin 31.00-1, October 1977, DeZurik.RTM. Series C Knife Gate Valves is a brochure published by DeZurik, a unit of General Signal, Sartell, Minn., 56377. At page 3, paragraph 12, this brochure shows a "vee-orifice valve" for throttling control of thick slurries such as paper stock.
U.S. Pat. No. 1,892,260 to Wick, dated Dec. 27, 1932, shows a pneumatic dash gun for applying a stucco finish, the gun including a storage receptacle for holding the mixture of sand, cement and water which is supplied through a valve into an air pipe for delivery through a nozzle. The valve comprises a plate containing a generally ovoid-shaped opening which is movable into and out of register with a circular cross section conduit leading from the storage receptacle.
German Offenlegungsschrift 1918875 published Nov. 6, 1969 by W. Hausammann et al also appears to disclose in FIG. 1 a valve in which a triangular port 27 is brought into and out of register with a circular orifice 17.
U.S. Pat. No. 1,550,725 to Jung dated Aug. 25, 1925, discloses a valve construction having a triangular port. (43 in FIG. 2) which aligns with a triangular shaped opening into a circular cross section orifice 31.
U.S. Pat. No. 4,471,942 to Kocanowski, dated Sep. 18, 1984 discloses a valve in which the cross-sectional flow area is defined by the coincidence of a circular aperture with a triangular apex.